This invention relates in general to an optical processor, and in particular to an optical amplifier with multiple functions.
In the information age, the demand for networks of higher and higher capacities grows relentlessly, at lower and lower costs. The demand is driven by many different factors. One of factors is that the tremendous growth of the Internet, and the World Wide Web has brought more and more users online, consuming bandwidth due to data transfers involving video and images. Also, businesses are relying increasingly on high speed intranets and extranets for their day-to-day operations. Furthermore, the ultimate vision of the information age is that information can be located anywhere but accessible from everywhere as if it were located locally. Networks of enormous capacity will be required to provide the infrastructure to realize this vision. All these factors are driving the need for more bandwidth in networks, which requires optical components as the system building blocks to be available in volume and at low cost.
FIG. 1 shows the building blocks of a prior art backward-pumped optical fiber amplifier 100. To achieve the desired functions for a typical amplifier, three branching components are used. The first branching component 102, comprising a wavelength division multiplexer and an isolator (WDM+Isolator), is used to couple the pump power in optical fiber 104 to the input erbium fiber 106 and isolate the unwanted back-flow signal from the components that are down stream from the WDM+Isolator 102. The input signal having radiation components in the bandwidth of about 1530 to 1620 nm is applied to input erbium fiber 106, and is amplified by the erbium in fiber 106 when stimulated by the pump power supplied by fiber 104 and reflected by WDM+Isolator 102. A 2% Tap Coupler 110 taps a small percentage of the amplified input signal from an optical output path of WDM+Isolator 102 for monitoring purposes. The other Wavelength Division Multiplexer (WDM ) 112 is used to merge an optical service channel 114 into the optical line 116. Splicing the above three components within the tight space usually allocated for the optical amplifier in fiberoptic applications is a formidable job
The present invention combines multiple branching functionalities into a compact package, which reduces the cost, size, labor and yet enhances the optical performance. The present invention presents component designs at low cost by integrating multiple functions into a single compact identity.
The multiple functions achieved by the various optical components in FIG. 1 includes amplifying an input optical signal by coupling pump power to an erbium fiber, isolating unwanted back-flow signal from components downstream from the amplifier and, optionally, merging an optical service signal into the output amplified signal.
This invention is based on the recognition that some or all of the above functions may be achieved by using a partially reflecting interface for the purpose of tapping a portion of the amplified input signal for monitoring purposes, while the remaining portion becomes the main output signal. A portion of the input signal that passes through or is reflected by the interface is the tapped signal that may then be used for monitoring purposes. Where such an interface is used as described above, an optional isolation function may be accomplished by means of an isolator in an optical path in the amplified input signal before such signal reaches the interface. This is an additional feature that may preferably be incorporated. In this manner, the optical path of the tapped signal need not pass through the isolator. The use of a partially reflective interface as described above enables a particularly compact package to be made which performs the above-described functions. The resulting package is smaller and cheaper than one of convention design and can be assembled with less labor, while its optical performance is enhanced over that of conventional designs.